skypac acoustic talk
DESCRIPTION
Acoustician Russ Cooper created this presentation to show the science behind the tuning of a hall.TRANSCRIPT
ACOUSTICS AND THE PERFORMING ARTS
Russ CooperJaffe Holden Acoustics
Norwalk, CTFEBRUARY 14, 2012
ACOUSTICS 101
WHAT IS SOUND?
CompressionExpansion
POINT SOURCE PRESSURE WAVES
PRESSURE WAVES FROM TUNING FORK
THE HUMAN EAR
EAR DRUM RESPONSE TO PRESSURE WAVES
PROPERTIES OF SOUND
90 dB
75 dB
SOUND ABSORPTIVE MATERIALS
SOUND REFLECTIVE MATERIALS
THE SCIENCE OF ACOUSTICS• Wallace Clement Sabine, the father of acoustics
uses organ pipes as sound sources and seat cushions in a Harvard University lab in 1898 to measure the properties of sound.
• Sabine goes on to assist in the design of Boston Symphony Hall in 1900, considered the best acoustics for a concert hall in the world
BOSTON SYMPHONY HALL
TYPICAL REVERBERATION TIME DECAY CURVE
Rt60 = V 20 S
Reverb Time = Volume Sound Absorption
0 2
60
0
Open Window 0
Acoustical Ceiling Tile
¾” Plaster On Lath
MATERIAL % REFLECTED % ABSORBED & TRANSMITTED
SOUND ABSORPTION COEFFICIENT
()
30
93
100
70
7
1.00
0.70
0.07
ABSORBED - TRANSMITTED - REFLECTED SOUND
SCIENTIFIC ACOUSTIC TERMS
• Reverberation Time: RT60
• Early Decay Time: EDT• Clarity: C80
• Inter-aural Cross Correlation: IACC• Bass Ratio (Warmth): BR• Direction of Reflection: LF• Initial Time Delay Gap: ITDG• Gain (Loudness): G• Noise Criteria: NC
ACOUSTIC DESIGN OF PERFORMANCE HALLS
SCIENCE OF ACOUSTICS• We can predict and model how individual sources
of sound radiating equally in all directions with equal energy levels at all frequencies will react at a given receiver position in a hall.
SCIENCE OF ACOUSTICS
• However, most performances involve multiple sources in different locations with varying radiation patterns and different energy levels at different frequencies.
SCIENCE OF ACOUSTICS
Equal Energy at every Frequency for Acoustic Model
Actual Musical Instruments – Varying Energy at Different Frequencies
ARTISTIC APPLICATION OF ACOUSTICS
• The art is in the application of the science•Experience with how sound should behave on stage in musical ensemble • Acoustic “Listening” – how the room will sound on
the stage, in the pit, in the orchestra seats, in the
balconies• Intuitive Auralization – The acoustician
must “hear” the drawings• Tuning the Hall to achieve the acoustic goals• Interaction of artists with the hall
ACOUSTICS FOR MULTI-USE HALLS
• Program, program, program• Acoustic Designs:
– Proscenium Style– Platform Forward– Concert Hall “Shaper”
• Adjustable Acoustic Systems– Draperies, Banners, Panels
• Integration of acoustic reflectors, lighting and sound
PROSCENIUM STYLE
PLATFORM FORWARD
CONCERT HALL “SHAPER”
SKYPAC ACOUSTIC GOALS
1. Classical Music:
2. Theatre / Dance / Opera:
• Warm, rich, enveloping• Clear & present• Well defined – blended, but distinct• Quiet Room• Excellent on-stage hearing
• Dry, but warm• Articulate & intelligible
3. Amplified Events:• Not too loud, room won’t “Overload”• No Echoes• Bass Control
ACOUSTIC CHALLENGES WITH VARIABLE PROGRAMS
Speech is Directional
Music and Speech have different acoustic requirements
ACOUSTIC CHALLENGES WITH VARIABLE PROGRAMS
Music and Speech have different acoustic requirements
Music is Omni-Directional
ACOUSTIC SOLUTION FOR MUSIC
• Utilizes reverberant stage house coupling for low frequencieslow frequencies
• Uses reflective shell for mid and high mid and high frequency frequency sound projection to audience and performers
• Light weight demountable orchestra shell in a stage house
Music: Light Weight Orchestra Shell
ADJUSTABLE ACOUSTICS FOR
PERFORMANCE SPACES
When is it needed?– Variable acoustic systems allow hall to
have different reverberation times– Can be used to control echoes from
loudspeakers– Can be used to “tune” the room for
different programs
Lecture Drama
Opera/Ballet Symphony
1.0 sec.
2.0 sec.
0.8 1.0
1.4
2.0Liveness (Rt)
Mid-frequency
Preferred
Experience Shows That AcousticsDiffer For Each Type of Performance
TYPES OF ADJUSTABLE ACOUSTIC SYSTEMS
• Velour Drapes - 25 to 32 ounce material on track or drum or winch line
• Hung in space or against a wall• Hidden behind sound transparent material
or scrim or exposed• Fiberglass or Felt or wool panels tracked or
on drum• Low frequency panel absorbers
ACOUSTIC CURTAINS
FABRIC COVERED TRACKING PANELS
Vertically tracking acoustical panels
CONCEALED ADJUSTABLE ACOUSTIC SYSTEM
Acoustic banners hidden behind perforated metal
WOOL BANNERS
ADJUSTABLE ACOUSTIC SYSTEMS
ADJUSTABLE ACOUSTIC SYSTEMS
POPULAR MUSIC ACOUSTIC CHALLENGES
ECHO
ADJUSTABLE ACOUSTIC SYSTEMS
VO
LUM
E/S
EA
T (
CU
BIC
FEET P
ER
PER
SO
N) 300
200
100
400
305360
CARNEGIE
HALL
BASS H
ALL0
LARGE VOLUME-TO-SEAT RATIO IS A CHARACTERISTIC OF ACOUSTICALLY
EXCELLENT HALLS
300312
BOSTON
SKYP
AC
25 20 15 10 5
GOOD
BETTER
BEST
QUIET NOISE LEVELS ARE A CHARACTERISTIC OF ACOUSTICALLY
EXCELLENT HALLS
NC- NOISE CRITERIA
HA
LL Q
UA
LIT
Y L
EV
EL
POINT OF DIMINISHING
RETURN
SKYPAC
RE
VE
RB
ER
ATIO
N T
IME
(SE
CO
ND
S)
1.5
1.0
0.5
2.0
0%
ADJUSTABLE ACOUSTICAL DRAPES OPTIMIZE SKYPAC REVERBERATION TIME
PERCENTAGEOF ABSORPTION INTRODUCED INTO HALL
50% 100%0
??2.5
??
??
1.6
1.45
1.3M
easu
red
Measu
red
Measu
red
Calc
ula
ted
Calc
ula
ted
Calc
ula
ted
CONSTRUCTION ISSUES THAT AFFECT THE ACOUSTICS
Holes in walls reduce the sound isolation between spaces
Poor installation of acoustic devices
No coordination of utility requirements and acoustic requirements
ACOUSTICAL TUNING
• Listening to the various ensembles to determine the correct setting of the adjustable acoustical systems
• Working with the music directors for proper musician placement on stage
• Operating all adjustable systems in the hall• Measuring the reverberation time in unoccupied
condition• Listening to the ensembles with full audience to
confirm settings• Measuring the reverberation time in occupied
condition
SKYPAC